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Whistles as potential indicators of stress in bottlenose dolphins (Tursiops truncatus)

UNCW Author/Contributor (non-UNCW co-authors, if there are any, appear on document)
H. Carter Esch (Creator)
The University of North Carolina Wilmington (UNCW )
Web Site:
Laela Sayigh

Abstract: Stress has been defined as an environmental effect on an individual that overtaxes its functional abilities. The diversity of stress responses among marine mammals makes it difficult to develop a comprehensive diagnostic protocol to evaluate stress. The development of a relatively non-invasive tool with which to evaluate stress in bottlenose dolphins (Tursiops truncatus) could allow for assessments of animals that may be at risk, and assessment of free-ranging animals without capture-release. The goal of this study was to evaluate whether vocalizations, specifically signature whistles, could serve as possible indicators of acute (or short-term) stress in bottlenose dolphins. Recordings made during brief capture-release events and during focal follows of undisturbed animals in Sarasota Bay, FL, were used to address this question. Although there is no evidence that capture-release events have any long or short term adverse impacts on members of the Sarasota dolphin community, it is likely that they are a source of short-term stress to the dolphins. I asked the following questions: Will whistle rates and number of loops (repetitive elements in whistles) be greater: (1) during capture-release than during undisturbed focal follows? (2) at the beginning of a capture-release session than at the end of a session? (3) during an individual’s first capture-release session than during later sessions? (4) when a mother is caught and released with a dependent calf than without a dependent calf? I also examined whether the duration of loops and/or inter-loop intervals, and maximum and minimum frequency of whistles change in any of the above contexts. Loop number was significantly higher during capture-release than during focal follows, and decreased significantly from the beginning to the end of an individual’s capture-release session. Loop duration was significantly shorter at the beginning than at the end of an individual session. Whistle rate was also significantly higher during capture-release than during focal follows, and during a dolphin’s first capture-release than during subsequent sessions. Females caught with a dependent calf produced whistles with significantly higher maximum frequencies and shorter inter-loop intervals than when caught and released without a dependent calf. Based on the results of this study, further research would be warranted on assessing the utility of signature whistle rate and loop number as behavioral indicators of short-term stress in bottlenose dolphins. These measures could potentially be utilized independently, or in conjunction with physiological indicators, in assessments of the impact of potentially stressful human activities on bottlenose dolphins.

Additional Information

A Thesis Submitted to the University of North Carolina at Wilmington in Partial Fulfillment of the Requirement for the Degree of Masters of Science
Language: English
Date: 2009
Bottlenose dolphin--Behavior, Bottlenose dolphin--Effect of stress on, Bottlenose dolphin--Florida--Sarasota, Bottlenose dolphin--Monitoring, Bottlenose dolphin--Vocalization
Bottlenose dolphin -- Behavior
Bottlenose dolphin -- Monitoring
Bottlenose dolphin -- Florida -- Sarasota
Bottlenose dolphin -- Vocalization
Bottlenose dolphin -- Effect of stress on